Corrosion-resisting protector cap

ABSTRACT

A device for protecting threaded shafts and nuts against corrosion. The device covers and protects a nut and the exposed portion of a threaded shaft from corrosion found in harsh environments by holding grease in place over the nut and shaft.

BACKGROUND—FIELD OF INVENTION

This invention relates to the field of fastenings made by nuts andthreaded shafts. More specifically, the invention comprises a devicewhich covers and protects a nut and exposed portion of a threaded shaftfrom corrosion found in harsh environments—such as saltwater immersion.The device substantially inhibits rusting of the nut itself and theexposed portion of the threaded shaft extending beyond the nut, allowingthe nut to be easily removed even after it has been left in place forsome time.

BACKGROUND—Description of Prior Art

Lug nut protective device are well known in the prior art. Many of theseprotective devices are theft deterrents. One such invention is disclosedin U.S. Pat. No. 4,521,146 to Wharton (1985). The Wharton patentdiscloses a wheel nut cover having threads which strip upon tighteningto create a tamper-resistant assembly. A similar device is disclosed inU.S. Pat. No. 4,786,224 to Wharton (1988). The '224 device includes aprotective shroud which fractures upon tightening, creating a similartamper-resistant assembly.

A device having similar objectives is disclosed in U.S. Pat. No.4,824,305 to McCauley (1989). The McCauley device actually substitutes adifferent type of lug nut for the standard type found on most automobileand trailer wheels. The lug nut has an internal cavity in a specialshape configured to receive a special type of removing tool. Without thetool, it is very difficult to remove the lug nut.

A simpler type of device is disclosed in U.S. Pat. No. 4,890,967 toRosenbaum (1990). The Rosenbaum device is not primarily concerned withtheft deterrence. Instead, its focus is to protect the lug stud and lugnut from corrosion. It attempts to accomplish this via covering the lugbolt's exposed surfaces (although the Rosenbaum disclosure illustrates alug bolt, it appears to be equally applicable to the more commonarrangement of a lug stud and lug nut). While somewhat effective forwarding off salt sprays and other corrosive environments, the '967device provides no positive seal to prevent water leaking into the coverupon immersion. As will be explained subsequently, water immersion is asignificant concern.

U.S. Pat. No. 5,380,070 (1995) discloses a domed plastic lug nut cover.Its stated purpose is to allow the securing of a wheel cover (“hub cap”)to a wheel without removing the lug nuts. The device actually threadsonto the exposed portion of a lug stud. Of course, since many lug studsdo not have threads extending past the lug nut, the '070 device will notwork in many applications. In addition, like the Rosenbaum device, the'070 device has no positive seal to prevent water leaking into the coverupon immersion.

U.S. Pat. No. 5,810,532 to Huang (1998) discloses another domed plasticlug nut cover. This particular device uses pliable spring clips tosecure itself to a lug nut. While potentially effective for one size oflug nut, different size clips would be required to accommodate the widevariety of lug nuts presently on the market. In addition, the Huangdevice also lacks any type of positive seal to prevent waterpenetration.

Another domed plastic cover is disclosed in U.S. Pat. No. 5,857,818 toBias (1999). This device uses the pliable nature of the material itselfto frictionally engage and hold itself to the hexagonal side walls of alug nut. Obviously, the device must be sized to fit a particular lugnut, raising the same concerns as seen for the Huang device. It alsolacks any type of water seal.

The lack of a water seal is a significant concern, especially where thedevice is to be used on boat trailer lug nuts. The lug nuts on boattrailers are always immersed completely in water when launching andretrieving a boat. If water is able to invade a protective lug nutcovering, it will often remain trapped there for several hours. Thisphenomenon causes significant corrosion, especially when the lug nut hasbeen immersed in salt water.

In addition, the protection of a nut locked on a threaded shaftobviously has applications far beyond the automotive industry. Manycoastal installations have nuts and threaded shafts exposed to a saltair environment. These typically become rusted and inoperable in amatter of months. Accordingly, the protection of a nut locked on athreaded shaft is a desirable objective.

The known devices for accomplishing this goal are limited in that they:

1. Must be particularly adapted to fit a specific nut;

2. Must be able to thread onto an exposed portion of the threaded shaft;

3. Require the use of springs or specialized tools to lock them inplace; and

4. Do not effectively protect against corrosion, especially followingwater immersion.

OBJECTS AND ADVANTAGES

Accordingly, several objects and advantages of the present invention areto provide a protective nut cover which:

1. Will accommodate a wide variety of nuts and shafts;

2. Does not require an exposed portion of thread to be held in place;

3. Does not require the use of springs or specialized tools to be lockedin place; and

4. Effectively protects against corrosion, especially following waterimmersion.

DRAWING FIGURES

FIG. 1 is an isometric view, showing a boat trailer.

FIG. 2 is a close-up view of the trailer wheel shown in FIG. 1.

FIG. 3 is an isometric view of the proposed invention.

FIG. 4 is an isometric view with cutaways, showing internal details ofthe proposed invention.

FIG. 5 is an isometric view with cutaways, showing the proposedinvention in place on a lug nut.

FIG. 5B is an isometric view with cutaways, showing the grease in theinternal cavity of the proposed invention.

FIG. 6 is an exploded isometric view showing a carriage bolt attaching ajoist to a piling.

FIG. 6B is an isometric view showing the same components as FIG. 6.

FIG. 6C is an isometric view showing the proposed invention in place onthe carriage bolt shown in FIG. 6.

FIG. 7 is an isometric view, showing a unified version of the protectorcap.

FIG. 8 is an isometric view, showing the unified version on a lug nut.

REFERENCE NUMERALS IN DRAWINGS

10 trailer

12 wheel

14 tire

16 lug stud

18 lug nut

20 protector cap

24 opening

26 inner portion

28 outer portion

30 grease

32 piling

34 joist

36 carriage bolt

38 washer

40 nut

42 unified protector cap

DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a typical boat trailer 10. Boat trailer 10 has atleast one pair of wheels 12 and tires 14. FIG. 2 illustrates the methodof attaching wheel 12 in more detail. Tire 14 is customarily mounted onwheel 12. Wheel 12 has a plurality of holes positioned to fit over lugstuds 16 (which are attached to the rotating portion of the trailer'saxle). Once wheel 12 is positioned with its mounting holes over lugstuds 16, a plurality of lug nuts 18 are threaded onto lug studs 16 inorder to secure wheel 12 in place. Those skilled in the art will knowthat lug studs 16 have external threads and lug nuts 18 havecorresponding internal threads. For purposes of visual clarity, thesethreads have not been illustrated.

When a lug nut 18 is tightened, a small threaded length of lug stud 16will typically protrude beyond lug nut 18. Those skilled in the art willreadily appreciate the fact that lug nuts and lug studs on boat trailersendure a particularly hostile environment. Returning briefly to thetrailer shown in FIG. 1, the reader will appreciate that in order tolaunch or recover a boat both wheels 12 must be immersed in water forextended periods of time. This immersion causes corrosion of lug nut 18and the exposed portion of lug stud 16. The problem is particularlyacute for saltwater operations, where significant corrosion can occur ina matter of hours.

Water immersion often causes the internal threads of lug nut 18 to rustand thereby bond with the external threads of lug stud 16. If thisprocess is allowed to continue, removal of lug nut 18 can becomeimpossible. Many users seek to remedy this problem by heavily greasingboth lug stud 16 and lug nut 18. Unfortunately, once the boat isrecovered and the trailer proceeds down the highway, centrifugal forcesgenerated in the rapidly spinning wheel tend to throw any applied greaseoff the surfaces needed protection. Thus, in order to be effective, thegrease must be constantly reapplied. The present invention seeksprimarily to eliminate this problem.

Returning now to FIG. 2, the reader will observe protector cap 20 inposition to be pushed over lug nut 18. In normal operation, lug nut 18would be secured in place. Protector cap 20 is then slipped over lug nut18. It is not necessary to loosen lug nut 18. Protector cap 20 can beapplied with lug nut 18 already tightened. A protector cap 20 is neededfor each lug nut 18. In the particular example shown, five protectorcaps 20 are needed.

FIG. 3 shows protector cap 20 in greater detail. For the particularexample shown, it is comprised of inner portion 26 and outer portion 28.The near end of inner portion 26 opens into opening 24. Opening 24 ismade significantly smaller than the nut protector cap 20 is intended tocover. The use of pliable material for protector cap 20 allows opening24 to expand over a particular nut and frictionally hold protector cap20 in place.

FIG. 4 shows a cutaway view of both inner portion 26 and out portion 28.The reader will observe that both portions are thin-walled hollowstructures. They are sized to be slipped together as indicated by thearrows. Both portions are made from pliable, high-friction materials sothey can frictionally engage and hold each other together. Moldingrubber is one example of an appropriate material for the two portions.Of course, protector cap 20 can also be made as a single piece. However,the use of two pieces allows the user to easily adjust the overalllength of the device in order to accommodate varying lengths of shaftsand nuts.

FIG. 5 is another cutaway view showing lug nut 18 tightened in place onlug shaft 16 (rotated upright for visual clarity). Portions of wheel 12,inner portion 26 and outer portion 28 have been cut away to aidvisualization. The reader will observe how inner portion 26 slips overand frictionally engages lug nut 18 (opening 24 is difficult to see inthe view, but it is found at the lowest extreme of inner portion 26).The reader will also observe how protector cap 20 can be placed over lugnut 18 without having to loosen lug nut 18.

In the particular example illustrated, lug shaft 16 does not protrudebeyond lug nut 18. Those skilled in the art will appreciate that manytypes of lug shafts do extend significantly beyond the lug nuts. Theexcess volume within protector cap 20 allows for this variation.

While protector cap 20 is held securely in place as shown, it is notcapable of excluding water and other contaminants without an addedcomponent. FIG. 5B illustrates this added component. The excess volumewithin protector cap 20 is filled with viscous grease 30 (shown in acutaway view, like the other components in FIG. 5B). Grease 30 isactually inserted into protector cap 20 before it is placed over lug nut18. When protector cap 20 is pushed into place, grease 30 is forced downand around lug nut 18 and lug shaft 16. The user can press outer portion28 into inner portion 26 in order to displace more grease if needed.This is generally done until a small amount of grease actually flows outof opening 24, thereby ensuing that the interior of protector cap 20 sicompletely bathed in grease.

Many different types of grease can be used. Marine greases, which aretypically formulated to resist water absorption, are particularlyeffective. Clear silicone greases also work quite well. Any type ofhighly viscous liquid which does not permit air and water to contact themetal surfaces of lug nut 18 and lug shaft 16 will suffice. Evensubstances which cure and become pliable solids may be used—such as blue“RTV” silicone.

Once grease 30 is placed within protector cap 20 and protector cap 20 isinstalled, it can remain in place indefinitely. It is not necessary toreplace grease 30 very often. Normal road use of the trailer will notloosen protector cap 20 and will not tend to displace the grease.

Although the use of protector cap 20 on an automotive lug nut is a goodapplication, it by no means constitutes the extent of the device'susefulness. Protector cap 20 can be used to protect any nut placed on athreaded shaft. The invention's application to a completely separateindustry is illustrated in FIG. 6. FIG. 6 shows a wooden piling 32 witha transverse notch cut into its top. Joist 34 is placed into thistransverse notch. Both piling 32 and joist 34 have a hole bored throughthem to accept carriage bolt 36. Carriage bolt 36 is placed within thehole and secured by washer 38 and nut 40, as shown in FIG. 6B.

This type of installation is typical in coastal home construction.Pilings are generally required for building on sand. The floor joistsare then secured to the pilings in the manner depicted in FIG. 6. Thesame type of fastening is used for docks, ramps, and all sorts of otherwooden structures. Unfortunately, once nut 40 is locked in place, theexposed portion of carriage bolt 36 and nut 40 rapidly begin to corrode.This corrosion often makes nut 40 impossible to subsequently remove.Worse still, the corrosion can advance to the point of rusting the boltin two.

FIG. 6C shows an elongated version of protector cap 20 in place on theexposed portion of carriage bolt 36 and nut 40. As in the automotiveapplication, the hollow interior of protector cap 20 is filled withhighly viscous grease.

Protector cap 20 is capable of protecting virtually any nut threadedonto an exposed shaft (allowing for different sizes, of course). The useof protector cap 20 significantly inhibits corrosion, allowing the nutto be easily removed from the shaft many years after it is installed.Additional applications for protector cap 20 would include automotivesuspension fastenings, axle shackle bolts, boat hardware, bridgefastenings, etc.

A two-piece protector cap 20 has been illustrated, and this version isparticularly suited to situations where the length of the exposed shaftis unknown. FIG. 6C is one such situation. As protector cap 20 is madeof a pliable material which can be cut with a knife, the user simplycuts outer portion 28 to the desired length. However, the reader caneasily appreciate that a one-piece protector cap would be simpler andmore convenient for those occasions where the required length is known.

FIG. 7 illustrates unified protector cap 42. FIG. 7 shows unifiedprotector cap 42 cut in half so that the reader may observe itsthin-walled structure. FIG. 8 shows unified protector cap 42 installedon a lug nut. The grease is placed in the interior of unified capprotector 42 in the same fashion as that described with respect to FIGS.5 and 5B.

Because unified cap protector 42 is simpler and cheaper to produce, itrepresents the preferred embodiment. However, the reader shouldunderstand that for those applications where the exposed shaft length isunknown (and the required length of the protector is therefore unknown),the two-piece version is preferable.

SUMMARY, RAMIFICATIONS, AND SCOPE

Accordingly, the reader will appreciate that the proposed inventionsignificantly inhibits corrosion in a nut threaded onto a shaft. Theinvention has further advantages in that it:

1. Will accommodate a wide variety of nuts and shafts;

2. Does not require an exposed portion of thread for securing itself inplace;

3. Does not require the use of the use of springs or specialized toolsto be locked in place; and

4. Effectively protects against corrosion, especially following waterimmersion.

Although the preceding description contains significant detail, itshould not be construed as limiting the scope of the invention butrather as providing illustrations of the preferred embodiment of theinvention. Thus, the scope of the invention should be fixed by thefollowing claims, rather than by the examples given.

Having described my invention, I claim:
 1. A device allowing a user toinhibit the corrosion of a nut and the exposed portion of a threadedshaft extending beyond said nut when said nut is threaded onto saidthreaded shaft, comprising: a. an inner portion, having a closed firstend, and an open second end, and a solid side wall connecting said firstend and said second end, and wherein said first end contains an openingsized to slip over and frictionally engage said nut, thereby holdingsaid inner portion to said nut; b. an outer portion, having an openfirst end and a closed second end, and a solid side wall connecting saidfirst end and said second end, wherein said outer portion is sized toslidably engage said inner portion by slidably engaging said open firstend of said outer portion with said open second end of said innerportion, so as to form a hollow interior within said inner portion andsaid outer portion having a length which is variable, depending on howfar said user pushes said outer portion into said slidable engagementwith said inner portion; and c. a highly viscous, corrosion-inhibitingliquid, placed within said hollow interior so as to coat and protectsaid nut and said exposed portion of said threaded shaft, wherein saidliquid is forced around said nut and said shaft as said user pushes saidouter portion further into said slidable engagement with said innerportion.
 2. The device as recited in claim 1, wherein saidcorrosion-inhibiting liquid is grease.
 3. The device as recited in claim1, wherein said corrosion-inhibiting liquid contains silicon.